function ajax(method, url, data, success) {
	var xhr = null;

	try {
		xhr = new XMLHttpRequest();
	}catch (e) {
		xhr = new ActiveXObject('Microsoft XMLHTTP')
	}

	if (method == 'get' && data) {
		url += '?' + data;
	}

	xhr.open(method, url, true);

	if (method == 'get') {
		xhr.send();
	} else {
		xhr.setRequestHeader('content-type', 'application/x-www-form-urlencoded');
		xhr.send(data);
	}

	xhr.onreadystatechange = function () {
		if (xhr.readyState == 4) {
			if (xhr.status == 200) {
				success && success(xhr.responseText);
			} else {
				alert('出错了,Err：' + xhr.status);
			}
		} 
	}
}